An update to the Baldur's Gate: Enhanced Edition Facebook page announces that voice actor Mark Meer has signed on to voice a character in the additional content being added to the RPG. My guess is that he's going to be the voice behind a prominent character that'll carry over to Baldur's Gate II: Enhanced Edition (to join his Throne of Bhaal voicing of Cyric), but we'll just have to wait and see:

We're happy to officially announce Mark Meer as one of our voice actors adding new content to the Baldur's Gate: Enhanced Edition.

Mark has previously appeared in the Baldur's Gate series and is best known for his work as Commander Shepard of Mass Effect fame.

"My name is Mark Meer and this is my favorite store in Ulgoth's Beard."